Donald Trump greets people in New York city in July. He calls himself a "clean hands freak" who hates shaking hands, and has written that he washes his hands thoroughly, and as much as possible. (Photo by Spencer Platt/Getty Images)

Jeb Bush is blasting his Republican rival Donald Trump for being a “germophobe” who hates shaking hands. For sure, it’s hard to be seen as friendly and accessible if you’re running for president and loathe pressing the flesh.

But as a way of avoiding infectious diseases, it’s not such a bad strategy.

[ The latest Jeb-Trump battle: Germophobia ]

Take the notoriously contagious norovirus, sometimes called “stomach flu.” This season, it might be even more sickening than usual because of a new strain that has emerged over the past year as a major cause of outbreaks in China, Japan and Australia.

That’s bad news not only for hand-shaking politicians, but also for places where noroviruses spread most easily: hospitals and nursing homes, university campuses and day-care centers, and cruise ships. The season typically starts in the fall and peaks in winter.

(Trump has called shaking hands "one of the curses of American society." He says he feels much better after thoroughly washing his hands, which he says he does as much as possible.)

For norovirus, a tiny amount — as little as 18 viral particles — on your food or your hand can make you sick. The virus inflames your stomach or intestines (or both), producing the all-too-familiar symptoms of stomach pain, diarrhea and vomiting. The main way that people get sick is from the fecal-oral route, including direct person-to-person contact.

That's why it's so important to wash hands after using the toilet. Unfortunately, many people don't do that.

Noroviruses are also pretty hardy. They can survive at freezing temperatures or above 140 degrees F, and for up to two weeks on surfaces.

Noroviruses are the leading cause of acute gastroenteritis in the United States. The bugs kill about 800 people and sicken up to  21 million Americans on an average year, according to the Centers for Disease Control and Prevention. Like flu, the virus mutates, and new strains emerge. But while flu typically mutates quickly, new norovirus strains tend to emerge only every two to four years. And when that happens, it’s not known whether preexisting immunity from exposure to other related noroviruses offers protection.

“Sometimes when there’s a new strain, we see much more widespread activity,” said Ben Lopman, a CDC epidemiologist who works with diarrheal diseases caused by viruses.

The new strain that has emerged elsewhere hasn’t been seen that often in the United States, he said, adding, “CDC will be monitoring outbreak activity in the forthcoming winter season in the United States through our national surveillance systems.”

Children are among the hardest hit by noroviruses. Increasingly, they seem to be getting infected at a young age. In the United States, virtually all children will get infected by age 5, and 80 percent of those are under age 2, Lopman said.

Here are some tips to prevent infection and reduce transmission:

• The single most important method is to wash your hands with soap and water for 20 seconds. Do it before eating, after using the bathroom and after changing diapers. Alcohol-based sanitizers generally do not appear as effective as soap and water, experts say. The bugs can be found in your vomit or stool even before you start feeling sick. Most people get better after about 48 hours, but the bug can stay in your stool for two weeks or more after you feel better.

• Don’t take care of others or prepare food if you’re sick and for at least two days after symptoms stop.

• Clean and disinfect contaminated surfaces. Use a chlorine bleach solution (5-25 tablespoons of household bleach per gallon of water) on hard, nonporous surfaces.

• Wash laundry thoroughly. Wear gloves while handling the contaminated items. Wash the items with detergent on the longest cycle and machine dry.

For politicians, maybe go with the elbow bump.

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